The 1918 24-Cent Inverted Jenny Plate Block, 1933 Double Eagle coin and 1856 British Guiana One-Cent Magenta are pictured in a provided image. (Photo courtesy of Sotheby’s) NEW YORK - "The holy grail of coins" and two of the world’s most valuable items in stamp-collecting are going up for auction next week in New York and could sell for a combined $37 million.The three items, an "elusive" 1933 Double Eagle Coin, the sole-surviving British Guiana One-Cent Magenta and a sheet of U.S.